请问怎样让div把select挡住？

Question

在《div》 里加个iframe
<div id="ZoneSelectDiv"
     style="position:absolute ;z-index : 200;visibility:hidden ;overflow:scroll; background-color: #eee;">
   <iframe src="javascript:false"
            style="position:absolute; visibility:inherit; top:0px; left:0px; width:100%; height:100%; z-index:-1; filter='progid:DXImageTransform.Microsoft.Alpha(style=0,opacity=0)';">
</iframe>
</div>